### Session GM: Microfluids: General IV: Bubbles, Drops and Particles

8:00 AM–10:10 AM, Monday, November 22, 2010
Long Beach Convention Center Room: 202B

Chair: Gaurav Soni, University of California, Santa Barbara

Abstract ID: BAPS.2010.DFD.GM.2

### Abstract: GM.00002 : Flow field inside a stationary microdroplet in a Hele-Shaw cell

8:13 AM–8:26 AM

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#### Authors:

Sungyon Lee
(LadHyX and department of Mechanics, Ecole Polytechnique)

Charles Baroud
(LadHyX and department of Mechanics, Ecole Polytechnique)

We consider the flow field inside a water drop held stationary in a flowing external oil, experimentally and theoretically. The droplet is strongly confined in the vertical direction, making it take a pancake"-like shape. It is anchored in place by introducing a local variation in the channel height which reduces the free surface energy, with minimal modifications to its general shape. Two contrasting flow regions are visible inside the drop: a fast recirculation flow is observed near the droplet boundary, while a slower flow takes place in the central region. While the central flow is well described by the standard Hele-Shaw model, the flow near the droplet edge displays strong three-dimensional recirculation, pointing to a complex hydrodynamic coupling between the droplet and outer flows. These two regimes are characterized for different droplet geometries and external flow rates, and a theoretical justification for their existence is provided.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.DFD.GM.2